Electrodes and stimulating devices are known as such in the prior art for different treatments of the human body. An example of an electrotherapy transducer is given in EP 0 638 330 which comprises a sheet of support material with a number of electrodes arranged in a matrix-like structure, adjacent electrodes receiving electric signals of opposite polarity. In a second embodiment, the structure of the electrodes is comb-shaped with electrodes being arranged alternately and equally spaced in relation to one another. This electrotherapy device is said to be used for the treatment of cellulitis or for the treatment of muscles but not much more information is given on the structure of the device, or on the electrical signals used during a treatment.
In the field of electrical stimulation, two stimulation principles are known: transcutaneous electrical nerve stimulation (TENS) on the one hand, and electrical muscular-type stimulation (EMS) on the other hand. TENS stimulation devices are used for the treatment of pain whereas EMS stimulation devices are used for physical therapy and body building, for example for correcting muscle atrophy, stimulating muscle growth and increasing range of motion.
Devices that apply such TENS and/or EMS stimulations to the body of a user are known per se in the art.
As an illustrative example, application EP 1 095 670 which is incorporated by reference in the present application, describes a neuromuscular electrical stimulator using stimulation electrodes and an electrical impulse generator. This device is mainly used for EMS stimulation and it comprises at least two electrodes spaced apart and placed on a part to be treated of the human body. A stimulator is connected to the electrodes through connection wires and it sends the desired electrical signals to the electrodes in order to stimulate the muscles.
With specific respect to TENS, this type of treatment has been extensively described in the art. As a reference, one may cite the publication “Electrotherapy 11th Edition Evidence-based practice”, October 2001 by Sheila Kitchen, MSc, PhD, DipTP, MSCP, Head, Division of Physiotherapy, King's College, London.
Chapter 17 of this publication relates to “Transcutaneous Electrical Nerve Stimulation (TENS)” by Mark Johnson, incorporated by reference in the present application, and reference is made to this Chapter for the theory and explanations relating to TENS treatments. As can be understood from this publication, TENS is “the most frequently used electrotherapy for pain relief, and reference is made to this publication for the theory explaining and demonstrating the effects of TENS stimulation and also the theory of “The Pain Gate”.
According to the above-mentioned article of Mark Johnson (see FIG. 17.2) under normal physiological circumstances, the brain generated pain sensations by processing incoming noxious information arising from stimuli such as tissue damage. The noxious information reaches the brain by passing through a metaphorical “pain gate” located in the lower levels of the central nervous system. The pain gate may be closed by activation of various sensory afferents, i.e. through rubbing the skin which generates activity in large diameter Aβ afferents which inhibits the onward transmission of noxious information.
It is therefore an aim of conventional TENS to selectively activate Aβ fibers using electrical currents to provide segmental analgesia.
Another way to close the pain gate is to activate pain-inhibitory pathways which originate in the brain and descend to the spinal cord through the brainstem. Accordingly, an aim of AL TENS (Acupuncture-like TENS) is to activate small diameter peripheral fibres to activate the descending pain-inhibitory pathways. This stimulation however provokes a muscle contraction.
Another way to produce peripheral blockade of nociceptive afferent activity and segmental and extrasegmental analgesia is to use Intense TENS to activate small diameter Aδ cutaneous afferents by delivering said TENS stimulation over peripheral nerves arising from the site of pain at an intensity which is just tolerable to the patient (using high-frequency and high-intensity currents).
During classical and Intense TENS stimulation programs, it is important to stimulate only the sensitive nerve cells end not the motor nerves, which will induce a tetanic muscle contraction which can be painful, an effect contrary to the one sought.
One of the problems to which the user of stimulators is confronted is the positioning of the electrodes on the body in view of the desired treatment and also the sizes of the electrodes used for a given treatment.
Another example of a stimulation device is given in US 2002/0077688. This publication relates to a body garment which is used in combination with an electrical muscle and/or nerve stimulation device. In this publication, the body garment is specifically structured to position the electrode pads at predetermined positions on the body corresponding with different muscle or nerve groups and it is connected to a TENS unit controller or an EMS unit controller for the desired stimulation. As taught in this document, the garment may cover the entire body of the user or only a part of said body.
Another publication of the prior art relating to TENS stimulation is WO 2005/002668. In this publication, the problem identified to be solved is adaptation. This occurs when although the amplitude and frequency of the stimulation are subjected to changes, the polarity of the electrodes is not changed so that the nerve cells which are subjected to the same stimulation adapt to said stimulation. Accordingly, an idea of this publication is to provide an electrode system with at least two poles which are separated by an insulating material to prevent a short-circuit between the poles and allowing the poles to be provided with electrical fields by stepwise alternating the negative current from one pole to the next pole. This causes two different areas to be stepwise treated by the electrode system. In one embodiment, the system includes four poles such that the electrical field may move between the poles. Since the action potential is initiated mainly below the negative pole, the treatment seems to wander over the surface covered by the electrode.
Another publication WO 2005/075018 relates to a device for neuromuscular stimulation. In this publication, the stimulation apparatus comprises a nerve stimulation array electrode comprising a substrate for application to the skin of a user bearing an array of electrodes arranged to be brought into electrical contact with the skin of the user, input contacts and user operable switch means for making or breaking the electrical contact between said input contacts and any selected one or ones of said electrodes allowing the user to freely form any group of electrodes. In addition, the apparatus comprises a separate common ground or counter electrode which will not generally need to be in the form of an array. This design allows in particular the practitioner or the patient to find which electrodes in the array contribute most effectively to producing the desired stimulation effect and he can thus form a specific group accordingly.
Another publication related to TENS treatment is WO 2005/065770. In this publication, the device comprises a current generating device configured to generate first and second types of electrical TENS currents. The construction allows a specific localized superficial blockade by an appropriate targeting of the intra epithelial and dermal nerves. More specifically, the device further comprises an array of electrodes to be placed around an injection location on the skin of a patient, said array being electrically coupled to the current generating device. The electrodes comprise a first and a second group, the first group being configured to be placed closer than the second group to the injection location on the skin of the patient. Typical sizes of electrodes are approximately 0.8 mm of width or diameter, an area of approximately 0.5 mm2 and the distance between the electrode is no more than 2 mm. Preferably, in this publication, the distance is less than 1 mm or even less than 0.5 mm. The current applying device is configured to apply the first type of TENS current to the first group of electrodes and apply the second type of TENS current to the second group of electrodes. By activating electrodes in pairs around the injection location, a ring of discharge pathways though the patient's skin may be sequentially created thereby providing a good coverage of the sensory nerves in the area. The voltage signals applied to the inner electrodes in particular may depolarize the nerves within the skin to thereby suppress pain sensitivity.
Other examples of TENS treatment devices and method are described in publications WO 93/22966, U.S. Pat. No. 5,785,040, U.S. Pat. No. 6,301,500 and US 2002/0055762. The content of all publications cited above are incorporated by reference in the present application.
Another field using electrodes applied to a patient is iontophoresis. This technique is generally defined as a non-invasive method of propelling high concentrations of a charged substance, normally medication or bioactive-agents, transdermally by repulsive electromotive force using a small electrical charge applied to an iontophoretic chamber containing a similarly charged active agent and its vehicle. Although using electrodes as well, this method and the devices used are in fact very different from methods and devices used in the field of TENS or EMS stimulation, in particular because of the effect sought and principle of functioning of the respective devices.
Such iontophoretic devices are used for example to inhibit perspiration from human hands, feet or underarms and also for the treatment of varied dermato logic and cosmetic problems.
Use of an iontophoretic device is for example described in U.S. Pat. No. 4,164,226. In this patent, the device comprises intermingled negative and positive electrodes (forming an array) all having porous material to carry out the iontophoretic effect.
WO 93/00959 shows another device and method to deliver topical drugs to an area of tissue to be treated by iontophoresis. In this publication the electrodes are made by two electrode patterns each including a set of substantially parallel electrodes being arranged in an alternating arrangement.
Other devices described in US 2002/055703 and U.S. Pat. No. 5,968,006 are used both for iontophoresis and electroporation. In both publications, an electrode structure has the shape of interdigitated comb-like electrode pairs. However, in such field, the use of electrodes is combined with a porous material or a chamber to carry out the iontophoretic effect and the electrical signal is not used to stimulate nerves or muscles as in a TENS or EMS system.